666564 has 12 divisors (see below), whose sum is σ = 1555344. Its totient is φ = 222184.

The previous prime is 666559. The next prime is 666599. The reversal of 666564 is 465666.

It is a tau number, because it is divible by the number of its divisors (12).

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

666564 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27762 + ... + 27785.

It is an arithmetic number, because the mean of its divisors is an integer number (129612).

2⁶⁶⁶⁵⁶⁴ is an apocalyptic number.

It is an amenable number.

666564 is an abundant number, since it is smaller than the sum of its proper divisors (888780).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

666564 is a wasteful number, since it uses less digits than its factorization.

666564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55554 (or 55552 counting only the distinct ones).

The product of its digits is 25920, while the sum is 33.

The square root of 666564 is about 816.4337082703. The cubic root of 666564 is about 87.3535618637.

The spelling of 666564 in words is "six hundred sixty-six thousand, five hundred sixty-four".